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N20 motors - Railway Modeller April 2018


Robin2
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I'm rather confused. The final drive shaft is of different diameters each side of the gear box. Am I correct in thinking that you have already removed this final drive shaft and replaced it, or that as you allude to in your last posting, this is your intention and that you are concerned about attempting to remove the D shaft? 

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Hello, the output  'D' shaft has a diameter of 3mm. the Markits-Romford axle is 3.18mm, or, 1/8". One of the 'box walls was slightly undersize, and the other was oversize. To overcome this disparity, I used a Romford axle bush onto the axle, which was an interference fit between the  axle, bush, and final gear. On the other wall, the oversize axle hole was remedied by soldering in the Romford axle bush. Both walls had another visit from the reamer, to keep them pretty much aligned.  Remember though, that the length of the bush is longer than the thickness of the 'box wall, by about 2mm. I filed off the excess to keep the overall width to 10mm. Judicious use of 1/8" washers will be needed to pack out the sideways thrust, or the final gear will lose mesh. 

  

 

Thank you for your post. I've had another look at the extracted 'D' shaft, and it should allow the shaft to be driven out from the smaller diameter, with the 'D' portion leading. 

 

Cheers,

Ian.

 

PS. Yes! Sorry! The photo shows the N20 gearbox, with a Markits-Romford  1/8" axle installed. 

Edited by tomparryharry
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10 minutes ago, Michael Edge said:

Why not use Markits 3mm axles?

 Well, I used what I had, and it's a happy coincidence that 3mm and 1/8" allowed a little bit of an interference fit.  I've been using 1/8" axles & bushes since I can't remember when, so it's a bit of a 'go to' situation. 3mm in a 1/8" hole is a sloppy fit, whereas right now, it's pretty good.  (at least for me ).

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  • 1 month later...
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The N20 motors are now being sold as a 'dual shaft' version. These retain the same 10mm width  across the gearbox wall sides. From a 00 perspective, they will still need to be taken apart to fit a suitable axle, but it's pretty good so far.

 

Michael Edge of this parish has suggested the Markits 3mm axle might be a suitable improvement. I haven't gone down that road yet, but I've ordered some of those motors today.  

 

Let's see!

 

Ian.

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  • 2 months later...

To add a little more to this thread, here is one of the type that tomparryharry introduced us to on the previous page fitted and in use in a scratchbuilt frame for a Hudswell Clarke diesel.

hcframes-001.jpg.b6257483e8c3f30036777cb72bd9ef40.jpg

 

HCfin-013.jpg.93899f89f289bda6a64fec676637deb6.jpg

 

One of the type that has the drive shaft under the motor fitted to scratchbuilt frames for a Drewry, driving through 0.4 module spur gears.

image.png.44acd580b69eb1415cb62c849520d5b6.png

 

image.png.6add4984331e34f98bb2e14db73e86e4.png

 

The in line type, fitted to a Craftsman etched brass Class 02 chassis and driving through nylon bevel gears.

image.png.f6c83593ada7a54137c79872a2ef2e6c.png

 

 

 

Edited by Ruston
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I have a dozen or so vehicles with plastic bevel gears (0.5 Mod) - non of which have given the slightest problem, also a few locos with smaller bevel gears (brass, loctited on, some epoxied) also with no problems.

My locos use much smaller gearmotors (less powerful) and still perform very well. The vehicles use N20s and need to work hard.

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2 hours ago, Michael Edge said:

Does this run fast enough? I've got some of these contrate gears but they aren't 1:1.

 

This one was timed at 70 mph at top speed using 12.3mm wheels and towing two replica coaches plus a black cat speed wagon. This was using the 1000rpm version. The biggest problem was traction with only one axle powered.

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On 17/07/2021 at 14:34, Ruston said:

To add a little more to this thread, here is one of the type that tomparryharry introduced us to on the previous page fitted and in use in a scratchbuilt frame for a Hudswell Clarke diesel.

hcframes-001.jpg.b6257483e8c3f30036777cb72bd9ef40.jpg

 

HCfin-013.jpg.93899f89f289bda6a64fec676637deb6.jpg

 

One of the type that has the drive shaft under the motor fitted to scratchbuilt frames for a Drewry, driving through 0.4 module spur gears.

image.png.44acd580b69eb1415cb62c849520d5b6.png

 

image.png.6add4984331e34f98bb2e14db73e86e4.png

 

The in line type, fitted to a Craftsman etched brass Class 02 chassis and driving through nylon bevel gears.

image.png.f6c83593ada7a54137c79872a2ef2e6c.png

 

 

 

May I ask from where are you sourcing your final drive gears? thanks.

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  • 3 weeks later...
On 16/01/2020 at 06:06, Giles said:

My experience would suggest that N20s are most effectively utilised with a 1:1 final drive if possible, and avoid a high ratio final drive (like wot I tried..)

 

5:1 N20 with 20:1 worm and gear

35588079606_b700b0938c_b.jpg

03B65D83-16E9-46C2-88CB-7D1F63F78992_zpsgmmk0e2a by giles favell, on Flickr

 

Not really, the only bad thing here is that particular implementation of worm drive. First the diameter of the worm. The worm rubs with a surface speed proportional to 3 times the diameter against the gear teeth, and with those fat worm teeth you risk contact on both sides of the gear tooth (which is not cut for worm drive to boot!) unless you keep it sloppy. And i don't remember those worms having a nice polished surface. Anybody remembering "running in" loco drives? In the hope the gear might polish the worm? Anyway, with the motor shaft the fastest piece in the drive train, this worm maximizes friction.

You need to keep worms as thin as possible and as slippery as possible, with matching, mating gears .

I'm confident you can connect any quality worm drive at any ratio to this n20 successfully.  Should there ever be a need.

 

Sorry,-w

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Well, I absolutely agree  (and I genuinely think it's great that you've taken the time to point this out) - this worm and gear (which were sold as Romfords matching set) are highly inefficient - right at the bottom end of the efficiency chart for worm and gears (for all the reasons you've rightly pointed out). A well engineered worm and gear can be very much more efficient - but still not as efficient as other forms of gearing. Escap for instance chose to use bevel gears as their primary drive between motor and Portescap gearbox - partly for space, but certainly for efficiency.

In Practice I find it much more satisfactory to use bevel gears to extract maximum efficiency, particularly when using smaller, less powerful motors than the N20s, where any shortfall shows more readily. My projects in recent years haven't seemingly needed running in, in consequence.

 

(P.s. I needed the 5:1 × 20:1 ratio on this, and couldn't find many options! MKll was a K20 bevel gear solution)

 

Best

 

Giles

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  • 2 months later...

Just to add a little bit heres something I'm playing around with which is an N20 driving a in this case a Corgi Q class London Trolleybus axle via plastic Bevel gears.

 The second axle has had its up and down movement extended and runs by friction on the road surface so all the Trolleybuses weight is sat on the driven axle. The Trolleybus will pick up the power from the overhead and be steered by an adaption of the Faller road systems.

 This was the lowest geared N20 and although the steering is yet to be done the bus runs up and down the work bench quite happily with the weight of the die cast body fitted.

I did have some video of it running but its telling me the file size is to large to down load but its very quiet in operation.

20211109_042806.jpg

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In road vehicles, the N20's are massively powerful, and well up to coping will a loaded 7mm artic. This is a Radio controlled Bedford TK converted from on of the Altaya models

 

IMG_1570

 

 

For 4mm vehicles, I find either 6mm gearmotors or in extremis 8mm perfectly able to cope (even with loaded lorries). This 4mm Bedford TK has a 6mm 100rpm gearmotor,  and I'd highly satisfactory. Motors via EBay 

 

2020-07-07_02-48-14 2021-04-22_16-20-25 M=B R=8 S=4

 

2020-07-07_02-48-34

 

 

Edited by Giles
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Now we're entering the realm of madness. 

 

@Londontram,  were you the gentlemen who had a trolleybus layout featured in the publications a number of years ago?  Or were you inspired by the same articles?   I was always impressed with the layout, though I forget which magazine, and what the name of the layout was.

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On 09/11/2021 at 15:17, AlfaZagato said:

Now we're entering the realm of madness. 

 

@Londontram,  were you the gentlemen who had a trolleybus layout featured in the publications a number of years ago?  Or were you inspired by the same articles?   I was always impressed with the layout, though I forget which magazine, and what the name of the layout was.

No not me I'm afraid I've just been insired as you say by previous Trolleybus layouts but as you can tell by the name and avitar I've long held an interest in public service street vehicles especially in London.

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On 09/11/2021 at 15:17, AlfaZagato said:

Now we're entering the realm of madness. 

 

@Londontram,  were you the gentlemen who had a trolleybus layout featured in the publications a number of years ago?  Or were you inspired by the same articles?   I was always impressed with the layout, though I forget which magazine, and what the name of the layout was.

Think you are remembering Walford Arches by the late Tony Chlad

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  • 2 months later...
On 23/03/2021 at 01:06, tomparryharry said:

I should say that this little fella is the first one I've modified. Putting back the gear train was a real PITA.  I'm now looking at a 'painless' way to drive out the D shaft, and re-insert with a Markits-Romford axle.  I just haven't had the courage (yet ) to take a press tool to it. The D shaft sleeve is a standard Markits-Romford 1/8" axle bush.

Is you process something like the following:

1. Remove shaft from housing, 

2. Press off drive gear, 

3. Replace shaft with one of desired diameter, 

4. Add a bush to support original drive gear, 

5. Stick it all back together?

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On 07/02/2022 at 01:42, Rod Hutchinson said:

Is you process something like the following:

1. Remove shaft from housing, 

2. Press off drive gear, 

3. Replace shaft with one of desired diameter, 

4. Add a bush to support original drive gear, 

5. Stick it all back together?

Hi Rod. Yes, that's basically it. I used a 1/8" Romford axle to replace the final gear axle, and re-assembled. If you're careful enough, there is a possibility to retain the 2 hollow rivets which pass through the gearbox.  If this is the case, it 'should' provide ability to accurately retain the motor on station.

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